Display panel and method of fabricating the same

ABSTRACT

A method of fabricating a display panel may include forming an oxide semiconductor pattern on a base layer including a first region and a second region, etching first, second, and third insulating layers to form a first groove that overlaps the second region, forming electrodes on the third insulating layer, forming a fourth insulating layer on the third insulating layer to cover the electrodes, thermally treating the fourth insulating layer, forming an organic layer to cover the fourth insulating layer, and forming an organic light emitting diode on the organic layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. non-provisional patent application claims priority under 35U.S.C. § 119 to Korean Patent Application No. 10-2017-0168681, filed onDec. 8, 2017, in the Korean Intellectual Property Office, the disclosureof which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The present disclosure relates to a display panel and a method offabricating the same, and in particular, to a highly reliable displaypanel and a method of fabricating the same.

A display panel includes a plurality of pixels and a driving circuit forcontrolling the pixels. The driving circuit of the display panel isconfigured to provide electrical control signals to the pixels.

Each of the pixels includes a pixel driving circuit and a display devicesuch as an organic light emitting diode (OLED) or a quantum-dotlight-emitting diode that is connected to the pixel driving circuit. Thepixel driving circuit includes at least one thin-film transistor and acapacitor. The thin-film transistor and the capacitor of the pixeldriving circuit control the display device, based on the electricalsignals received from one or more driving circuits of the display panel.According to required electric characteristics, the pixel drivingcircuit may be configured to include two or more thin-film transistorscontaining at least two different semiconductor materials andproperties. The pixel driving circuit including two or more thin-filmtransistors may drive the pixel in a more stable, more reliable manner.

SUMMARY

An embodiment of the inventive concept provides a method of stablyfabricating a display panel.

An embodiment of the inventive concept provides a highly-reliabledisplay panel.

According to an embodiment of the inventive concept, a method offabricating a display panel may include forming a silicon semiconductorpattern on a base layer including a first region and a second regionthat is extended from the first region, the silicon semiconductorpattern overlapping the first region, forming a first control electrodeon the silicon semiconductor pattern, the first control electrodeoverlapping the silicon semiconductor pattern with a first insulatinglayer interposed therebetween, forming a second control electrode tooverlap the first region and to be spaced apart from the first controlelectrode with a second insulating layer interposed therebetween,forming an oxide semiconductor pattern on the second control electrodeto overlap the second control electrode with a third insulating layerinterposed therebetween, etching the first, second, and third insulatinglayers to form a first contact hole and a second contact hole exposingat least a portion of the silicon semiconductor pattern and a firstgroove that overlaps the second region, forming on the third insulatinglayer a first input electrode and a first output electrode that areconnected to the silicon semiconductor pattern through the first andsecond contact holes, and a second input electrode and a second outputelectrode that are connected to the oxide semiconductor pattern, forminga fourth insulating layer on the third insulating layer to cover thefirst input electrode, the first output electrode, the second inputelectrode, and the second output electrode, thermally treating thefourth insulating layer, forming on the organic layer an organic layerto cover the fourth insulating layer, and forming an organic lightemitting diode that is connected to the first output electrode.

In an embodiment, the thermal treating of the fourth insulating layermay be performed at a temperature of about 300° C. or higher.

In an embodiment, the organic layer may include polyimide.

In an embodiment, the etching of the first, second, and third insulatinglayers may be performed to simultaneously form the first and secondcontact holes and the first groove using a single mask.

In an embodiment, the method may further include forming a second groovethat overlaps the first groove in the fourth insulating layer after theforming of the fourth insulating layer. The organic layer may be formedto fill the first groove and the second groove.

In an embodiment, the method may further include forming an inorganiclayer between the first insulating layer and the base layer. The formingof the second groove may include forming a third groove that overlapsthe first groove in the inorganic layer.

In an embodiment, the method may further include forming a third contacthole in the organic layer to expose a portion of the first outputelectrode, forming a connection electrode on the organic layer to beconnected to the first output electrode through the third contact hole,and forming an upper organic layer on the organic layer to cover theconnection electrode. The organic light emitting diode may be connectedto the connection electrode through the upper organic layer.

In an embodiment, the connection electrode may be formed of a materialthat is different from the first output electrode.

In an embodiment, the connection electrode may be formed of a materialwhose resistance is lower than that of the first output electrode.

In an embodiment, the forming of the first input electrode, the firstoutput electrode, the second input electrode, and the second outputelectrode may include forming a conductive layer on the third insulatinglayer to cover the oxide semiconductor pattern and patterning theconductive layer using an etching gas. The etching gas may contain afluoro compound.

In an embodiment, the conductive layer may have a higher etch rate thanthe oxide semiconductor pattern in the patterning of the conductivelayer using the etching gas.

According to an embodiment of the inventive concept, a display panel mayinclude a base layer including a first region and a second region thatare bent from the first region around a specific bending axis, a firstthin-film transistor disposed in the first region, the first thin-filmtransistor including a crystalline silicon semiconductor pattern, afirst control electrode, and a first input electrode and a first outputelectrode that are coupled to the crystalline silicon semiconductorpattern and are spaced apart from each other with the first controlelectrode interposed therebetween, a second thin-film transistordisposed in the first region to have a bottom gate structure, the secondthin-film transistor including a second control electrode, an oxidesemiconductor pattern disposed on the second control electrode, and asecond input electrode and a second output electrode that are in contactwith the oxide semiconductor pattern and are spaced apart from eachother, a passivation layer disposed in the first region and the secondregion to cover the first thin-film transistor and the second thin-filmtransistor and to include a first groove that overlaps the secondregion, a plurality of inorganic layers disposed between the passivationlayer and the base layer to include a second groove that overlaps thefirst groove, an organic layer disposed in the first region and thesecond region and on the passivation layer to cover inner surfaces ofthe first and second grooves, and an organic light emitting diodedisposed on the organic layer and in the first region and electricallyconnected to the first thin-film transistor. Etch rates of the secondinput electrode and the second output electrode that are etched by afluoro compound may be higher than that of the oxide semiconductorpattern.

In an embodiment, the second input electrode and the second outputelectrode may include molybdenum.

In an embodiment, the display panel may further include an upper organiclayer disposed between the organic layer and the organic light emittingdiode, and a connection electrode disposed between the upper organiclayer and the organic layer and coupled to each of the organic lightemitting diode and the first output electrode. The connection electrodeincludes a material that is different from that of the first outputelectrode.

In an embodiment, the connection electrode may include a material whoseresistance is lower than that of the first output electrode.

In an embodiment, the display panel may further include a signal linethat is disposed in the second region and overlaps the first groove andthe second groove. The signal line may be disposed on the same layer asthe connection electrode.

In an embodiment, a plurality of inorganic layers may be disposed toexpose a portion of a top surface of the base layer, and the organiclayer may be disposed to be in contact with the portion of the topsurface of the organic layer.

In an embodiment, the display panel may further include a pixeldefinition layer disposed on the organic layer to define an opening, Theorganic light emitting diode may be disposed in the opening. The pixeldefinition layer may overlap the first region and the second region andmay include an organic material.

In an embodiment, the pixel definition layer may include a recessedportion on an inner surface the opening.

In an embodiment, the display panel may further include a signal linethat is disposed in the second region and overlaps the first groove andthe second groove. The signal line may be disposed on the same layer asthe second output electrode.

In an embodiment, the signal line may include a plurality of patternsthat are disposed in the second region and are spaced apart from eachother in a direction crossing the bending axis.

In an embodiment, the passivation layer may be in contact with the oxidesemiconductor pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will be more clearly understood from the followingbrief description taken in conjunction with the accompanying drawings.The accompanying drawings represent non-limiting, example embodiments asdescribed herein.

FIGS. 1A and 1B are perspective views illustrating a display panelaccording to an embodiment of the inventive concept.

FIG. 2 is a plan view of a display panel shown in FIG. 1A.

FIG. 3A is an equivalent circuit diagram of a pixel according to anembodiment of the inventive concept.

FIGS. 3B and 3C are sectional views, each illustrating a portion of thepixel of FIG. 3A.

FIGS. 4A to 4C are sectional views, each illustrating a bending regionof a display panel according to an embodiment of the inventive concept.

FIG. 5 is a sectional view illustrating a region of a display panelaccording to an embodiment of the inventive concept.

FIG. 6 is a sectional view illustrating a region of a display panelaccording to an embodiment of the inventive concept.

FIGS. 7A to 7Q are sectional views illustrating a process of fabricatinga display panel according to an embodiment of the inventive concept.

FIG. 8A is a graph showing current-voltage characteristics of athin-film transistor according to a comparative example.

FIG. 8B is a graph showing current-voltage characteristics of athin-film transistor according to an embodiment of the inventiveconcept.

FIG. 9 is a sectional view illustrating a portion of a display panelaccording to an embodiment of the inventive concept.

FIGS. 10A to 10D are sectional views illustrating a method offabricating a display panel according to an embodiment of the inventiveconcept.

It should be noted that these figures are intended to illustrate thegeneral characteristics of methods, structure, and/or materials utilizedin certain example embodiments and to supplement the written descriptionprovided below. These drawings are not, however, to scale and may notprecisely reflect the precise structural or performance characteristicsof any given embodiments, and should not be interpreted as defining orlimiting the range of values or properties encompassed by exampleembodiments. For example, the relative thicknesses and positioning ofmolecules, layers, regions, and/or structural elements may be reduced orexaggerated for clarity. The use of similar or identical referencenumbers in the various drawings is intended to indicate the presence ofa similar or identical element or feature.

DETAILED DESCRIPTION

Example embodiments of the inventive concepts will now be described morefully with reference to the accompanying drawings, in which exampleembodiments are shown.

FIGS. 1A and 1B are perspective views illustrating a display panelaccording to an embodiment of the inventive concept. FIG. 2 is a planview of a display panel shown in FIG. 1A. FIG. 1A illustrates a displaypanel DP in an unfolded state, and FIG. 1B illustrates the display panelDP, at least a portion of which is in a bent state. Hereinafter, anembodiment of the inventive concept will be described with reference toFIGS. 1A to 2.

Referring to FIGS. 1A and 1B, the display panel DP may be provided tohave a front surface DP-FS that is oriented parallel to a firstdirection DR1 and a second direction DR2. The front surface DP-FS mayinclude a display region DP-DA and a peripheral region DP-NDA. Thedisplay region DP-DA may be a region of the front surface DP-FS that isused to display an image. A thickness of the display panel DP may bemeasured in a third direction DR3 perpendicular to the first and seconddirections DR1 and DR2.

The peripheral region DP-NDA may be adjacent to the display regionDP-DA. In an embodiment, the peripheral region DP-NDA may be providedalong a border of the display region DP-DA to enclose the display regionDP-DA. In an embodiment, the peripheral region DP-NDA may include aportion that is disposed adjacent to a bending region, whose width issmaller than that of the display region DP-DA when measured in thesecond direction DR2. Thus, the portion of the peripheral region DP-NDAhaving a reduced width may reduce a bending area of the display panelDP.

The display panel DP may include at least a portion that is bent. Thedisplay panel DP may be classified into a first region NBA (hereinafter,a non-bending region) and a second region BA (hereinafter, a bendingregion). The bending region BA may be defined at a relatively narrowregion of the display panel DP, when measured in the second directionDR2.

When the bending region BA is in a bent state, the bending region BA mayinclude a curvature region CA that is bent with a specific curvature anda facing region FA that is provided to face the non-bending region NBA.The non-bending region NBA, the curvature region CA, and the facingregion FA may be arranged in the first direction DR1. The bending regionBA may be bent around a bending axis BX extending in the seconddirection DR2. For example, the curvature region CA of the bendingregion BA may be bent around the bending axis BX, and the facing regionFA of the bending region BA may be placed to face a portion of thenon-bending region NBA in the third direction DR3.

Referring to FIG. 2, the display panel DP may include a plurality ofpixels PX, a plurality of signal lines SGL, and a driving circuit GDC.The plurality of pixels PX and the plurality of signal lines SGL may beprovided on the front surface DP-FS.

The pixels PX may be provided in the display region DP-DA. In anembodiment, the display region DP-DA is illustrated to have a tetragonalor rectangular shape, but the inventive concept is not limited thereto.Each of the pixels PX may be configured to display light having aspecific color. The pixels PX may be classified into a plurality ofgroups, according to colors of lights to be emitted therethrough. Forexample, the pixels PX may include red pixels, green pixels, and bluepixels. In certain embodiments, the pixels PX may further include whitepixels. Even when pixels are included in different groups, the pixeldriving circuits of the pixels may be configured to have the samestructure.

The driving circuit GDC may be provided in the peripheral region DP-NDA.The peripheral region DP-NDA may be adjacent to the display regionDP-DA. In an embodiment, the peripheral region DP-NDA is illustrated toenclose the display region DP-DA, but the inventive concept is notlimited thereto.

The driving circuit GDC may include a gate driving circuit. The gatedriving circuit may be configured to generate a plurality of gatesignals and sequentially output the gate signals to a plurality of gatelines GL to be described below. In certain embodiments, the gate drivingcircuit may be configured to output other control signals that aredifferent from the gate signals to the pixels PX.

The gate driving circuit may include a plurality of thin-filmtransistors that are formed by the same process as that for the pixeldriving circuit of the pixels PX (e.g., by a low temperaturepolycrystalline silicon (LTPS) process or a low temperaturepolycrystalline oxide (LTPO) process).

The signal lines SGL may include gate lines GL, data lines DL, a powerline PL, and a control signal line CSL. Each of the gate lines GL andeach of the data lines DL may be connected to corresponding ones of thepixels PX. The power line PL may be connected to the pixels PX. Thecontrol signal line CSL may be configured to deliver the control signalsto a scan driving circuit. The driving circuit GDC may include the scandriving circuit.

The signal lines SGL may be connected to signal pads DP-PD,respectively. Some of the signal lines SGL (e.g., the control signalline CSL, the data line DL, and the power line PL) may be extended fromthe non-bending region NBA to the bending region BA and may be connectedto the respective ones of the signal pads DP-PD. The signal pads DP-PDmay be electrically connected to a circuit substrate that may beexternally provided. The signal pads DP-PD may be provided in the facingregion FA of the bending region BA.

In an embodiment, the display panel DP may further include a drivingchip that is connected to the data lines DL. Here, the driving chip maybe directly mounted on the display panel DP, and ones of the signal padsDP-PD that are connected to the data lines DL may be connected to thedriving chip. The structure of the display panel DP may be variouslychanged, and the inventive concept is not limited to a specificstructure of the display panel DP.

FIG. 3A is an equivalent circuit diagram of a pixel according to anembodiment of the inventive concept. FIGS. 3B and 3C are sectionalviews, each illustrating a portion of the pixel of FIG. 3A. Forconvenience in illustration, one of the pixels PX is exemplarilyillustrated in FIG. 3A. Hereinafter, the pixel PX will be described inmore detail with reference to FIGS. 3A to 3C. For concise description,an element previously described with reference to FIGS. 1A to 2 may beidentified by the same reference number without repeating an overlappingdescription thereof.

As shown in FIG. 3A, the pixel PX may be connected to a correspondingone of the data lines DL, a corresponding one of the gate lines GL, andthe power line PL. For example, the pixel PX may include an organiclight emitting diode or a quantum-dot light-emitting diode. Aluminescent layer of the organic light emitting diode may include anorganic luminescent material. A luminescent layer of the quantum-dotlight-emitting diode may include quantum dots and quantum rods. For thesake of simplicity, the following description will refer to an examplein which the pixel PX includes an organic light emitting diode.

The pixel PX may include a first thin-film transistor T1, a secondthin-film transistor T2, a capacitor Cst, and an organic light emittingdiode OLED. The first thin-film transistor T1, the second thin-filmtransistor T2, and the capacitor Cst may constitute a pixel drivingcircuit for driving the organic light emitting diode OLED. In certainembodiments, the pixel driving circuit may further include at least onemore thin-film transistor or at least one more capacitor, in addition tothe first thin-film transistor T1, the second thin-film transistor T2,and the capacitor Cst, but the inventive concept is not limited thereto.

The first thin-film transistor T1 may be connected to the organic lightemitting diode OLED. The first thin-film transistor T1 may be used tocontrol a driving current flowing through the organic light emittingdiode OLED, depending on an amount of electric charges stored in thecapacitor Cst. The second thin-film transistor T2 may be connected tothe gate line GL and the data line DL. The second thin-film transistorT2 may be configured to output a data signal from the data line DL tothe capacitor Cst, in response to a gate signal applied to the gate lineGL. An amount of electric charges to be stored in the capacitor Cst maybe determined by a difference between a voltage corresponding to thedata signal that is output from the second thin-film transistor T2 and afirst power voltage ELVDD that is transmitted through the power line PL.

A turn-on time of the first thin-film transistor T1 may be determineddepending on the amount of charges stored in the capacitor Cst. Theorganic light emitting diode OLED may be configured to emit light, whenthe first thin-film transistor T1 is in a turn-on period. The color(i.e., wavelength) of light emitted from the organic light emittingdiode OLED may be determined by a material of a light-emitting pattern.For example, the organic light emitting diode OLED may be configured toemit light of red, green, blue, or white color, but the inventiveconcept is not limited thereto.

A sectional structure of the pixel PX will be described with referenceto FIGS. 3B and 3C. Here, FIG. 3B illustrates a region of the pixel PX,in which the first thin-film transistor T1, the second thin-filmtransistor T2, and the organic light emitting diode OLED are provided,and FIG. 3C illustrates another region of the pixel PX, in which thefirst thin-film transistor T1, the second thin-film transistor T2, theorganic light emitting diode OLED, and the capacitor Cst are provided.That is, FIGS. 3B and 3C illustrate two different regions of the samepixel PX, respectively.

As shown in FIGS. 3B and 3C, the display panel DP may include a baselayer BL, a circuit device layer DP-CL, a display device layer DP-OLED,and an encapsulation layer TFE. The base layer BL, the circuit devicelayer DP-CL, the display device layer DP-OLED, and the encapsulationlayer TFE may be stacked in the third direction DR3.

The base layer BL may be a layer, film, or plate, on which the firstthin-film transistor T1, the second thin-film transistor T2, and thecapacitor Cst are formed. The base layer BL may include a plasticsubstrate, a glass substrate, a metal substrate, or a compositesubstrate including organic and/or inorganic materials. The plasticsubstrate may include a synthetic resin layer. The synthetic resin layermay include a thermosetting resin. The synthetic resin layer may be apolyimide-based resin layer, but the inventive concept is not limited toa specific material. For example, the synthetic resin layer may includeat least one of acryl resins, methacryl resins, polyisoprene resins,vinyl resins, epoxy resins, urethane resins, cellulose resins, siloxaneresins, polyamide resins, and perylene resins.

The base layer BL may define a planar shape of the display panel DP. Forexample, a shape of the display panel DP shown in FIG. 1A may correspondto a planar shape of the base layer BL. Accordingly, the base layer BLmay include the non-bending region NBA, the bending region BA includingthe curvature region CA and the facing region FA, and a portion of thebase layer BL corresponding to the bending region BA may be bent aroundthe bending axis BX.

The circuit device layer DP-CL may be provided on the base layer BL. Thecircuit device layer DP-CL may include a pixel driving circuit and aplurality of insulating layers. For example, the circuit device layerDP-CL may be configured to include a barrier layer BRL, a buffer layerBFL, and first to sixth insulating layers 10, 20, 30, 40, 50, and 60, inaddition to the first thin-film transistor T1, the second thin-filmtransistor T2, and the capacitor Cst.

The barrier layer BRL may be provided to cover a top surface of the baselayer BL. The barrier layer BRL may be configured to prevent acontamination material from permeating into the circuit device layerDP-CL and the display device layer DP-OLED through the base layer BL.The barrier layer BRL may include a silicon oxide layer and a siliconnitride layer. The silicon oxide layer and the silicon nitride layer maybe alternatingly stacked on the base layer BL.

The buffer layer BFL may be provided on the barrier layer BRL. Thebuffer layer BFL may be configured to allow conductive patterns orsemiconductor patterns to be more tightly bonded to the base layer BL.Therefore, the conductive patterns and the semiconductor patterns may bestably formed on the buffer layer BFL provided in the display panel DP,compared to a structure of the pixel in which the conductive patternsand semiconductor patterns are directly formed on the top surface of thebase layer BL without the buffer layer BFL. The buffer layer BFL may beformed of or include at least one of inorganic and organic materials.The buffer layer BFL may include a silicon oxide layer and a siliconnitride layer. The silicon oxide layer and the silicon nitride layer maybe stacked alternatingly. In certain embodiments, at least one of thebuffer layer BFL and the barrier layer BRL may be omitted.

A first semiconductor pattern OSP1 may be provided on the buffer layerBFL. The first semiconductor pattern OSP1 may be formed of or include acrystalline semiconductor material. For example, the first semiconductorpattern OSP1 may be formed of or include a polycrystalline semiconductormaterial (e.g., poly silicon).

The first semiconductor pattern OSP1 may include an input region and anoutput region that are doped with impurities, and a channel region thatis provided between the input and output regions. In FIGS. 3B and 3C,the input and output regions are illustrated with a hatched pattern, forconvenience in illustration.

The input region may be coupled to a first input electrode DE1, and theoutput region may be coupled to a first output electrode SE1. Thechannel region of the first semiconductor pattern OSP1 may be providedbetween the input region and the output region and may overlap a firstcontrol electrode GE1, when viewed in a plan view. According to the typeof the impurities, the first semiconductor pattern OSP1 may be of p orn-type conductivity. According to the type of the first semiconductorpattern OSP1, electrons or holes may flow as majority carriers in thechannel region.

The channel region of the first thin-film transistor T1 may be formed ofor include a polycrystalline semiconductor material. Thus, the firstthin-film transistor T1 may be used as a driving device with highmobility and high reliability.

The first insulating layer 10 may be provided on the first semiconductorpattern OSP1. The first insulating layer 10 may be formed of or includeat least one of inorganic and organic materials. For example, the firstinsulating layer 10 may be formed of or include silicon nitride and/orsilicon oxide.

The first insulating layer 10 may be provided on the buffer layer BFL tocover at least a portion of the first semiconductor pattern OSP1.However, the inventive concept is not limited thereto, and in certainembodiments, the first insulating layer 10 may be provided in aninsulating pattern that overlaps at least the channel region of thefirst semiconductor pattern OSP1. The shape of the first insulatinglayer 10 may be variously changed, and the inventive concept is notlimited to a specific shape of the first insulating layer 10.

The first control electrode GE1 and a first capacitor electrode E1 ofthe capacitor Cst may be provided on the first insulating layer 10. Inan embodiment, the first control electrode GE1 may be provided on thesame layer as the first capacitor electrode E1.

The first control electrode GE1 may overlap at least the channel regionof the first semiconductor pattern OSP1. The first control electrode GE1may be spaced apart from the first semiconductor pattern OSP1 with thefirst insulating layer 10 interposed therebetween. In an embodiment, thefirst insulating layer 10 may serve as a gate insulating layer of thefirst thin-film transistor T1.

The first capacitor electrode E1 may be used as one of two electrodes ofthe capacitor Cst. In an embodiment, the first capacitor electrode E1and the first control electrode GE1 may correspond to two parts of asingle conductive pattern. In certain embodiments, the first controlelectrode GE1 and the first capacitor electrode E1 may correspond to twoseparate patterns that are electrically connected to each other by anadditional bridge electrode (not shown), or that are electricallydisconnected from each other and are applied with different voltages,respectively.

The second insulating layer 20 may be provided on the first controlelectrode GE1 and the first capacitor electrode E1. The secondinsulating layer 20 may be provided on the first insulating layer 10 tocover the first control electrode GE1 and the first capacitor electrodeE1.

The second insulating layer 20 may be formed of or include at least oneof inorganic and organic materials. The second insulating layer 20 mayinclude a material that is different from that of the first insulatinglayer 10. For example, the second insulating layer 20 may include ametal oxide material (e.g., aluminum oxide), and the first insulatinglayer 10 may include silicon nitride and/or silicon oxide. However, theinventive concept is not limited thereto, and in certain embodiments,the second insulating layer 20 may be formed of or include the samematerial as that of the first insulating layer 10. The second insulatinglayer 20 may be used to protect the first insulating layer 10 in asubsequent process (e.g., for forming a second control electrode GE2)and thus to prevent the first semiconductor pattern OSP1 that isprovided below the first insulating layer 10 from being damaged.

The second control electrode GE2 of the second thin-film transistor T2,an upper electrode UE, and a second capacitor electrode E2 of thecapacitor Cst may be provided on the second insulating layer 20. Thesecond control electrode GE2 may not overlap the first control electrodeGE1, when viewed in a plan view. In an embodiment, the second controlelectrode GE2 may be provided on a layer that is different from a layerprovided under the first control electrode GE1.

The upper electrode UE may overlap the first control electrode GE1, whenviewed in a plan view. In a case where the upper electrode UE and thefirst control electrode GE1 are applied with different voltages, theupper electrode UE and the first control electrode GE1 may serve aselectrodes of a capacitor. In certain embodiments, in a case where theupper electrode UE and the first control electrode GE1 are applied withthe same voltage, the upper electrode UE, along with the first controlelectrode GE1, may be used as a gate electrode for controlling aswitching (i.e., on/off) operation of the first thin-film transistor T1or an electric potential of the channel region of the firstsemiconductor pattern OSP1.

The second capacitor electrode E2 may overlap the first capacitorelectrode E1, when viewed in a plan view. The second capacitor electrodeE2 may be spaced apart from the first capacitor electrode E1 with thesecond insulating layer 20 interposed therebetween, thereby forming thecapacitor Cst.

In an embodiment, the upper electrode UE, the second capacitor electrodeE2, and the second control electrode GE2 may be provided on the samelayer. For example, the upper electrode UE, the second capacitorelectrode E2, and the second control electrode GE2 may be simultaneouslyformed by a single patterning process using the same mask. Accordingly,the upper electrode UE, the second capacitor electrode E2, and thesecond control electrode GE2 may be formed of or include the samematerial and may have substantially the same stacking structure. Incertain embodiments, the upper electrode UE may be omitted.

The third insulating layer 30 may be provided on the second insulatinglayer 20. The third insulating layer 30 may be provided to cover the topsurface of the second insulating layer 20, the top surface of the upperelectrode UE, the top surface of the second control electrode GE2, andthe top surface of the second capacitor electrode E2. The thirdinsulating layer 30 may serve as a gate insulating layer of the secondthin-film transistor T2.

The third insulating layer 30 may be an inorganic layer and/or anorganic layer and may have a single- or multi-layered structure. Forexample, the third insulating layer 30 may be an inorganic layer that isformed of or includes at least one of aluminum oxide, titanium oxide,silicon oxide, silicon oxynitride, zirconium oxide, and hafnium oxide.For example, the third insulating layer 30 may be a single silicon oxidelayer.

A second semiconductor pattern OSP2 of the second thin-film transistorT2 may be provided on the third insulating layer 30. The secondsemiconductor pattern OSP2 may be formed of or include at least one ofoxide semiconductors. For example, the oxide semiconductors may includemetal oxides, whose metallic element is at least one of zinc (Zn),indium (In), gallium (Ga), tin (Sn), and titanium (Ti), or may include amixture of zinc (Zn), indium (In), gallium (Ga), tin (Sn), and titanium(Ti), and an oxide thereof. In certain embodiments, the secondsemiconductor pattern OSP2 may include a crystallized oxidesemiconductor. The crystallized oxide semiconductor may be provided tohave a vertical directionality.

The second semiconductor pattern OSP2 may include an input region and anoutput region that are doped with impurities, and a channel region thatis provided between the input region and the output region. In FIGS. 3Band 3C, the input and output regions of the second semiconductor patternOSP2 are illustrated with a hatched pattern, for convenience inillustration. The input region may be coupled to a second inputelectrode DE2, and the output region may be coupled to a second outputelectrode SE2. The channel region of the second semiconductor patternOSP2 may be provided between the input region and the output region andmay overlap the second control electrode GE2, when viewed in a planview. According to the type of the impurities, the second semiconductorpattern OSP2 may be of p or n-type conductivity. According to the typeof the second semiconductor pattern OSP2, electrons or holes may flow asmajority carriers in the channel region.

A reduced metal material may be used as the impurities in the secondsemiconductor pattern OSP2. For example, the input region and the outputregion may contain a metallic material that is reduced from a metaloxide material constituting the channel region, thereby reducing aleakage current of the second thin-film transistor T2, and thus, thesecond thin-film transistor T2 may be used as a switching device havingan improved on-off property.

The first input electrode DE1 and the first output electrode SE1 of thefirst thin-film transistor T1 and the second input electrode DE2 and thesecond output electrode SE2 of the second thin-film transistor T2 may beprovided on the third insulating layer 30. In an embodiment, the firstinput electrode DE1, the first output electrode SE1, the second inputelectrode DE2, and the second output electrode SE2 may be simultaneouslyformed by a single patterning process using the same mask. Accordingly,the first input electrode DE1, the first output electrode SE1, thesecond input electrode DE2, and the second output electrode SE2 may beformed of or include the same material and may have the same stackingstructure. For example, the first input electrode DE1, the first outputelectrode SE1, the second input electrode DE2, and the second outputelectrode SE2 may be formed of or include molybdenum.

A first contact hole CH1 and a second contact hole CH2 may be formed toexpose a portion of the input region and the output region of the firstsemiconductor pattern OSP1, respectively, and the first input electrodeDE1 and the first output electrode SE1 may be coupled to the firstsemiconductor pattern OSP1 through the first and second contact holesCH1 and CH2, respectively. The first contact hole CH1 and the secondcontact hole CH2 may be formed to penetrate through the first to thirdinsulating layers 10, 20, and 30.

The second input electrode DE2 and the second output electrode SE2 maybe directly coupled to the second semiconductor pattern OSP2. The secondinput electrode DE2 and the second output electrode SE2 may be coupledto two opposite ends of the second semiconductor pattern OSP2,respectively. At least a portion of the second input electrode DE2 maybe directly provided in the input region of the second semiconductorpattern OSP2, and at least a portion of the second output electrode SE2may be directly provided in the output region of the secondsemiconductor pattern OSP2. In the second thin-film transistor T2, eachof the second input electrode DE2 and the second output electrode SE2may be coupled to the second semiconductor pattern OSP2, without anyportion provided in a contact hole.

The fourth insulating layer 40 may be provided on the third insulatinglayer 30 to cover the first input electrode DE1, the first outputelectrode SE1, the second input electrode DE2, and the second outputelectrode SE2. The fourth insulating layer 40 may be an organic orinorganic layer and may have a single- or multi-layered structure.

In an embodiment, the fourth insulating layer 40 may be an inorganiclayer that is formed of or includes at least one of aluminum oxide,titanium oxide, silicon oxide, silicon oxynitride, zirconium oxide, andhafnium oxide. For example, the fourth insulating layer 40 may be asilicon oxide layer. The fourth insulating layer 40 may be referred toas “a passivation layer”.

In an embodiment, the fourth insulating layer 40 may be formed through athermal treatment process. For example, the thermal treatment processmay be performed at a high temperate of 300° C. or higher, andresultantly, the fourth insulating layer 40 may be cured with defects. Adetailed description thereof will be omitted.

The fifth insulating layer 50 may be provided on the fourth insulatinglayer 40. The fifth insulating layer 50 may be an organic layer. Forexample, the fifth insulating layer 50 may be formed of or include apolymer resin such as polyimide.

A connection electrode CNE may be provided on the fifth insulating layer50. The connection electrode CNE may be connected to the first outputelectrode SE1 of the first thin-film transistor T1 through a thirdcontact hole CH3 that is formed to penetrate through the fourthinsulating layer 40 and the fifth insulating layer 50.

The connection electrode CNE may be formed of or include a material thatis different from the first input electrode DE1, the first outputelectrode SE1, the second input electrode DE2, and the second outputelectrode SE2. For example, the connection electrode CNE may be formedof or include a material whose electric resistance is lower than thoseof the first input electrode DE1, the first output electrode SE1, thesecond input electrode DE2, and the second output electrode SE2. In thiscase, a contact resistance between the organic light emitting diode OLEDand the first thin-film transistor T1 may be reduced, thereby improvingelectric characteristics of the display device.

However, the inventive concept is not limited to the above example, andin certain embodiments, the connection electrode CNE may be formed of orinclude the same material as the first input electrode DE1, the firstoutput electrode SE1, the second input electrode DE2, and the secondoutput electrode SE2. In certain embodiments, the connection electrodeCNE may be omitted, and the organic light emitting diode OLED and thefirst thin-film transistor T1 may be directly coupled to each other. Thestructure of the display panel DP may be variously changed, and theinventive concept is not limited to a specific structure of the displaypanel DP.

The sixth insulating layer 60 may be provided on the fifth insulatinglayer 50 to cover the connection electrode CNE. The sixth insulatinglayer 60 may be an organic layer and may have a single- or multi-layeredstructure.

In an embodiment, the fifth insulating layer 50 and the sixth insulatinglayer 60 may be a polyimide resin layer having a single-layeredstructure. However, the inventive concept is not limited thereto, and incertain embodiments, the fifth insulating layer 50 and the sixthinsulating layer 60 may include at least one of acryl resins, methacrylresins, polyisoprene resins, vinyl resins, epoxy resins, urethaneresins, cellulose resins, siloxane resins, polyamide resins, andperylene resins.

The organic light emitting diode OLED may be provided on the sixthinsulating layer 60. A first electrode AE of the organic light emittingdiode OLED may be provided on the sixth insulating layer 60. The firstelectrode AE may be connected to the connection electrode CNE through afourth contact hole CH4 that is formed to penetrate through the sixthinsulating layer 60.

A pixel definition layer PDL may be provided on the sixth insulatinglayer 60. The pixel definition layer PDL may have an opening OP that isformed to expose at least a portion of the first electrode AE. Theopening OP of the pixel definition layer PDL may define a light-emittingregion PXA of each pixel. For example, a plurality of the pixels PX maybe regularly arranged on a flat surface of the display panel DP (e.g.,see FIG. 1A). Regions in which the pixels PX are provided may be definedas ‘pixel regions’, and each of the pixel regions may include thelight-emitting region PXA and a non-light-emitting region NPXA adjacentto the light-emitting region PXA. The non-light-emitting region NPXA mayenclose the light-emitting region PXA.

A hole control layer HCL may be commonly provided in the light-emittingregion PXA and the non-light-emitting region NPXA. A common layer suchas the hole control layer HCL refers to a layer that is commonlyprovided in a plurality of the pixels PX. The hole control layer HCL mayinclude a hole transport layer and a hole injection layer.

A light-emitting pattern EML may be provided on the hole control layerHCL. The light-emitting pattern EML may be locally provided in a regioncorresponding to the opening OP. The light-emitting pattern EML may bedivided into a plurality of separate patterns that are respectivelyformed in the pixels PX.

In an embodiment, the light-emitting pattern EML is illustrated to havea patterned structure, but in certain embodiments, the light-emittingpattern EML may be provided to have a continuous structure spanning aplurality of the pixels PX. Here, the light-emitting pattern EML may beconfigured to generate a white-color light. In addition, thelight-emitting pattern EML may be provided to have a multi-layeredstructure.

An electron control layer ECL may be provided on the light-emittingpattern EML. The electron control layer ECL may include an electrontransport layer and an electron injection layer. A second electrode CEmay be provided on the electron control layer ECL. The electron controllayer ECL and the second electrode CE may be commonly provided in theplurality of pixels PX.

The encapsulation layer TFE may be provided on the second electrode CE.The encapsulation layer TFE may be provided to commonly cover aplurality of the pixels PX. In an embodiment, the encapsulation layerTFE may be provided to directly cover the second electrode CE. Incertain embodiments, a capping layer may be provided to cover the secondelectrode CE. The capping layer may be an organic layer. In anembodiment, an inorganic layer that is formed by a sputtering method maybe additionally formed on the capping layer. In an embodiment, astacking structure of the organic light emitting diode OLED may have ashape obtained by capsizing the stacking structure of the organic lightemitting diode OLED that is illustrated in FIG. 3B.

The encapsulation layer TFE may include at least one of an inorganiclayer and an organic layer. In an embodiment, the encapsulation layerTFE may include two inorganic layers and an organic layer therebetween.In an embodiment, the encapsulation layer TFE may include a plurality ofinorganic layers and a plurality of organic layers that are alternatelystacked.

The inorganic encapsulation layer may protect the organic light emittingdiode OLED from moisture or oxygen, and the organic encapsulation layermay be provided to protect the organic light emitting diode OLED fromforeign substances (e.g., dust particles) and to provide a flat topsurface. The inorganic encapsulation layer may include a silicon nitridelayer, a silicon oxynitride layer, a silicon oxide layer, a titaniumoxide layer, or an aluminum oxide layer, but the inventive concept isnot limited thereto. The organic encapsulation layer may include anacrylic organic layer, but the inventive concept is not limited thereto.

FIGS. 4A to 4C are sectional views, each illustrating a bending regionof a display panel according to an embodiment of the inventive concept.Each of FIGS. 4A to 4C illustrates a section of the curvature region CAof FIG. 2 taken parallel to the first and third directions DR1 and DR3.FIGS. 4A and 4C illustrate a region on which a signal line SL or SL-PTare provided, and FIG. 4B illustrates another region on which the signalline is not provided. A signal line SL extending in the first directionDR1 is illustrated in FIG. 4A, and the signal line SL-PT that includes aplurality of patterns spaced apart from each other in the firstdirection DR1 are illustrated in FIG. 4C. Hereinafter, an embodiment ofthe inventive concept will be described in more detail with reference toFIGS. 4A to 4C. For concise description, an element previously describedwith reference to FIGS. 1A to 3C may be identified by the same referencenumber without repeating an overlapping description thereof.

As shown in FIGS. 4A to 4C, the bending region BA may have a stacking orsectional structure similar to that of the first region NBA (e.g., seeFIG. 1A). The barrier layer BRL, the buffer layer BFL, and the first tosixth insulating layer 10 to 60 may be sequentially provided on the topsurface of the base layer BL.

The barrier layer BRL and/or the buffer layer BFL may be provided todefine a groove GV-1 (hereinafter, a first groove) that overlaps thebending region BA. The first groove GV-1 may be defined within thecurvature region CA. The first groove GV-1 may extend along thecurvature region CA or in a second direction (not shown). A width of thebase layer BL that is exposed by the first groove GV-1 and is measuredin the first direction DR1 may be less than a width of the curvatureregion CA in the first direction DR1.

The first to fourth insulating layers 10 to 40 may be provided to definea groove GV-2 (hereinafter, a second groove) that overlaps the bendingregion BA. The second groove GV-2 may be defined within the curvatureregion CA. The first to fourth insulating layers 10 to 40 may beprovided to partially expose a top surface of the inorganic layersincluding the barrier layer BRL and the buffer layer BFL.

Side surfaces of the barrier layer BRL and the buffer layer BFL definingthe first groove GV-1 may be inclined at an angle with respect to thetop surface of the base layer BL, when viewed in a sectional view. Sidesurfaces of the first to fourth insulating layers 10 to 40 defining thesecond groove GV-2 may also be inclined at an angle with respect to thetop surface of the base layer BL, when viewed in a sectional view. Theinclined angles of the first groove GV-1 and the second groove GV-2 maybe the same or different.

The fifth insulating layer 50 may be provided to cover the first regionNBA (e.g., see FIG. 1A) and may be extended from the non-bending regionNBA to cover the bending region BA. Here, in the bending region BA, thefifth insulating layer 50 may be provided to fill the first groove GV-1and the second groove GV-2. The fifth insulating layer 50 may be incontact with the top surface of the base layer BL that is exposed by thefirst groove GV-1, the inclined surface of the first groove GV-1, andthe inclined surface of the second groove GV-2. The fifth insulatinglayer 50 may be in contact with a portion of the top surface of thebuffer layer BFL that is not covered with the first to fourth insulatinglayers 10 to 40.

In an embodiment, the number of stacked insulating layers in thecurvature region CA may be reduced by providing the first groove GV-1and the second groove GV-2 in the curvature region CA. The more theinsulating layers provided in the curvature region CA, the easierdefects such as delamination or buckling may occur by a bending stress.According to an embodiment of the inventive concept, since the number ofthe stacked insulating layers provided in the curvature region CA isreduced, the curvature region CA may be easily bent without causingdefects.

In an embodiment, the first groove GV-1 and the second groove GV-2 mayremove the barrier layer BRL, the buffer layer BFL, and the first tofourth insulating layers 10, 20, 30, and 40 in the curvature region CA.As described above, the barrier layer BRL, the buffer layer BFL, and thefirst to fourth insulating layers 10, 20, 30, and 40 may includeinorganic materials. According to an embodiment of the inventiveconcept, by removing the inorganic layers from the curvature region CA,it may be possible to prevent or suppress the inorganic layers frombeing damaged by a bending stress.

In an embodiment, since the first groove GV-1 and the second groove GV-2are filled with an organic layer (e.g., the fifth insulating layer 50),it may be possible not only to prevent a crack from propagating throughthe inorganic layer, but also to improve flexibility of the curvatureregion CA. Since the fifth insulating layer 50 that is provided in thenon-bending region NBA is used to fill the first groove GV-1 and thesecond groove GV-2, it may be possible to simplify a fabrication processand a device structure of the display panel DP.

As shown in FIG. 4A, at least a portion of the signal line SL may beprovided on the fifth insulating layer 50. The sixth insulating layer 60may be provided to cover and protect the signal line SL. The signal lineSL may correspond to at least one of the signal lines SGL connected tothe signal pads DP-PD (e.g., see FIG. 2). For example, the signal lineSL may be a data line or a power line. In certain embodiments, thesignal line SL may be provided on a layer that is different from a layerunder the signal lines SGL and the signal pads DP-PD, and may be used asa bridge line connecting the signal lines SGL and the signal pads DP-PDto each other.

Although not shown in FIG. 4A, another portion of the signal line SL(e.g., provided in the display region DP-DA) may be provided on adifferent layer. For example, the signal line SL may include anotherportion that is provided on the third insulating layer 30. These twodifferent portions of the signal line SL may be connected to each otherthrough a contact hole that is formed to penetrate through the fourthinsulating layer 40 and the fifth insulating layer 50. The contact holemay be formed in the peripheral region DP-NDA of the non-bending regionNBA.

In an embodiment, at least one of layers that are provided in thedisplay region DP-DA may be extended to cover at least a portion of thetop surface of the sixth insulating layer 60. In certain embodiments,the sixth insulating layer 60 may not be provided in the curvatureregion CA.

As shown in FIG. 4B, the curvature region CA may include a region, inwhich the signal line SL is not provided. In such a region without thesignal line SL, the sixth insulating layer 60 may be in contact with thefifth insulating layer 50 or may cover the top surface of the fifthinsulating layer 50.

As shown in FIG. 4C, the signal line SL-PT may be a patterned signalline including a plurality of patterns. The patterns of the patternedsignal line SL-PT may be spaced apart from each other in the firstdirection DR1. When viewed in a plan view, the patterns of the patternedsignal line SL-PT may be connected to each other by a pattern extendingin the second direction DR2 (e.g., see FIG. 1A) within other region thatis not shown in FIG. 4C. The patterned signal line SL-PT may allow aportion extending in a direction perpendicular to the bending axis BX(e.g., see FIG. 1B) to have a reduced area, and thereby reducing abending stress to be exerted on the patterned signal line SL-PT.

FIG. 5 is a sectional view illustrating a region of a display panelaccording to an embodiment of the inventive concept. FIG. 5 illustratesboth a portion of the non-bending region NBA and a portion of thebending region BA. For example, in FIG. 5, the portion of thenon-bending region NBA may include a light-emitting region PXAcorresponding to the light-emitting region PXA shown in FIG. 3B, and theportion of the bending region BA may include a region corresponding tothat of FIG. 4C. For concise description, an element previouslydescribed with reference to FIGS. 1A to 4C may be identified by the samereference number without repeating an overlapping description thereof.

As shown in FIG. 5, the display panel DP may further include a thirdgroove GV-3 formed in the bending region BA. The second groove GV-2 maybe defined in the first to third insulating layers 10, 20, and 30, andthe third groove GV-3 may be defined in the fourth insulating layer 40.A portion of the fourth insulating layer 40 that overlaps the secondgroove GV-2 may be removed to form the third groove GV-3.

A width of the third groove GV-3 in the first direction DR1 may belarger than that of the second groove GV-2 in the first direction DR1.In addition, the width of the third groove GV-3 in the first directionDR1 may be larger than that of the first groove GV-1 in the firstdirection DR1. The first to third grooves GV-1, GV-2, and GV-3 may besequentially formed in the third direction DR3 to form a staircasestructure.

The fifth insulating layer 50 may be provided to fill the first to thirdgrooves GV-1, GV-2, and GV-3 or to cover an inner surface of each of thefirst to third grooves GV-1, GV-2, and GV-3. In an embodiment, thedisplay panel DP may be designed to have only an organic layer (e.g.,the fifth insulating layer 50) in at least a center portion of thecurvature region CA by forming the first to third grooves GV-1, GV-2,and GV-3 and filling them with the organic layer.

As shown in FIG. 5, the connection electrode CNE may be used as a signalline passing through the curvature region CA. In the non-bending regionNBA, the connection electrode CNE may be configured to connect the firstoutput electrode SE1 of the first thin-film transistor T1 to the firstelectrode AE of the organic light emitting diode OLED.

The connection electrode CNE may be interposed between the fifthinsulating layer 50 and the sixth insulating layer 60 and may beprovided to pass through the non-bending region NBA and the bendingregion BA. The connection electrode CNE may be used as a bridge patternconnecting a conductive pattern that is provided in the non-bendingregion NBA to a conductive pattern that is provided in a facing region(not shown). In an embodiment, the connection electrode CNE may includea plurality of patterns that are provided in the curvature region CA andare spaced apart from each other in the first direction DR1. In thiscase, the connection electrode CNE may prevent a crack or disconnectionfrom occurring by a bending stress.

In certain embodiments, a pixel definition layer PDL-H may be providedto have a recessed portion RS that is formed around or near an openingregion defining the light-emitting region PXA. For example, a mask and aspacer supporting the mask may be used in a deposition process forforming the light-emitting pattern EML, and the formation of therecessed portion RS may result from the use of the mask or the spacer.The display panel DP having the recessed portion RS may prevent thelight-emitting pattern EML or the light-emitting region PXA from beingdamaged by the mask. The recessed portion RS may be formed by a process,in which a halftone mask is used. According to an embodiment of theinventive concept, the pixel definition layer PDL-H is used to form thelight-emitting pattern EML without an additional process, therebyreducing a process cost and simplifying a fabrication process.

In an embodiment, at least one or each of the fifth insulating layer 50,the sixth insulating layer 60, and the pixel definition layer PDL-H mayinclude an organic material. A stacking structure that overlaps thecurvature region CA may be designed to include only organic materials,thereby improving flexibility of the display panel DP at the curvatureregion CA and achieving high reliability of the display panel DP evenwhen a folding/unfolding operation is repeated.

FIG. 6 is a sectional view illustrating a region of a display panelaccording to an embodiment of the inventive concept. For convenience indescription, a region corresponding to FIG. 3B is illustrated in FIG. 6.For concise description, an element previously described with referenceto FIGS. 1A to 5 may be identified by the same reference number withoutrepeating an overlapping description thereof.

As shown in FIG. 6, the display panel DP may further include a lightblocking pattern LSP that is provided between the fifth and sixthinsulating layers 50 and 60 and overlaps the second semiconductorpattern OSP2.

The light blocking pattern LSP may be formed of or include a materialhaving high absorptivity or high reflectance. The light blocking patternLSP may be provided over the second semiconductor pattern OSP2 toprevent a fraction (e.g., a reflected fraction) of light that isgenerated in the organic light emitting diode OLED from being incidentinto the second semiconductor pattern OSP2.

The light blocking pattern LSP may be formed of or include the samematerial as that of the connection electrode CNE. For example, the lightblocking pattern LSP may be formed of or include a metallic material.The light blocking pattern LSP may have the same stacking structure asthe connection electrode CNE. The light blocking pattern LSP and theconnection electrode CNE may be simultaneously formed by a singlepatterning process using the same mask, thereby simplifying thefabrication process and reducing the process cost.

FIGS. 7A to 7Q are sectional views illustrating a process of fabricatinga display panel according to an embodiment of the inventive concept. Forcomparison, two regions corresponding to FIGS. 3B and 4A are illustratedin each of FIGS. 7A to 7Q. For concise description, an elementpreviously described with reference to FIGS. 1A to 6 may be identifiedby the same reference number without repeating an overlappingdescription thereof.

As shown in FIG. 7A, at least one inorganic layer may be formed on thebase layer BL. The at least one inorganic layer may overlap both of thenon-bending region NBA and the bending region BA. Although not shown,during the fabrication process, the base layer BL may be placed on aworking substrate. The working substrate may be removed after thefabrication of the display panel.

The at least one inorganic layer may be formed by depositing, coating,or printing an inorganic material on the base layer BL. In anembodiment, the at least one inorganic layer may include the barrierlayer BRL and the buffer layer BFL, as shown in FIG. 7A. The formationof the barrier layer BRL may include sequentially forming a siliconoxide layer and a silicon nitride layer on the base layer BL. Theformation of the buffer layer BFL may include sequentially forming asilicon oxide layer and a silicon nitride layer on the barrier layerBRL.

As shown in FIG. 7A, a first preliminary semiconductor pattern OSP1-Pmay be formed on the buffer layer BFL. The first preliminarysemiconductor pattern OSP1-P may be formed of or include a siliconsemiconductor material. The formation of the first preliminarysemiconductor pattern OSP1-P may include forming a semiconductor layerand then patterning the semiconductor layer. In an embodiment, thesemiconductor layer may be crystalized before or after the patterning ofthe semiconductor layer.

Thereafter, as shown in FIG. 7B, the first insulating layer 10 may beformed in the non-bending region NBA and the bending region BA to coverthe buffer layer BFL and the first preliminary semiconductor patternOSP1-P. The first insulating layer 10 may be formed by a deposition,coating, or printing process. At least one or each of other insulatinglayers that will be formed on the first insulating layer 10 may beformed using one of the deposition, coating, and printing processes.

The first control electrode GE1 may be formed on the first insulatinglayer 10. The formation of the first control electrode GE1 may includeforming a conductive layer on the first insulating layer 10 and thenpatterning the conductive layer. The first capacitor electrode E1 (e.g.,see FIG. 3C) of the capacitor Cst may be formed using the same processas that for the first control electrode GE1.

Next, a doping process may be performed on the first preliminarysemiconductor pattern OSP1-P using the first control electrode GE1 as amask. In the doping process, impurities may be injected into the firstpreliminary semiconductor pattern OSP1-P through the first insulatinglayer 10, as depicted by the arrow. Here, the impurities may not beinjected into a channel region of the first preliminary semiconductorpattern OSP1-P that overlaps the first control electrode GE1, whereasthe impurities may be injected into both side regions (i.e., an inputregion and an output region) of the first preliminary semiconductorpattern OSP1-P that are spaced apart from each other with the channelregion interposed therebetween. In an embodiment, the input and outputregions of the first preliminary semiconductor pattern OSP1-P may bedoped with n-type dopants (e.g., group V elements). The firstsemiconductor pattern OSP1 may be formed by doping the first preliminarysemiconductor pattern OSP1-P. However, the inventive concept is notlimited to the above example, and in certain embodiments, the firstsemiconductor pattern OSP1 may be formed by doping the first preliminarysemiconductor pattern OSP1-P with p-type dopants (e.g., group IIIelements).

Thereafter, as shown in FIG. 7C, the second insulating layer 20 may beformed in both of the non-bending region NBA and the bending region BAto cover the first insulating layer 10 and the first control electrodeGE1. The second control electrode GE2 that does not overlap the firstcontrol electrode GE1 may be formed on the second insulating layer 20.For example, when viewed in a plan view, the second control electrodeGE2 may be spaced apart from the first control electrode GE1. The secondcontrol electrode GE2 and the upper electrode UE may be formed using thesame process. Although not shown, the second capacitor electrode E2(e.g., see FIG. 3C) of the capacitor Cst may be formed by the sameprocess as that for the second control electrode GE2 and the upperelectrode UE.

Thereafter, as shown in FIG. 7D, the third insulating layer 30 may beformed in the non-bending region NBA and the bending region BA to coverthe second insulating layer 20, the second control electrode GE2, andthe upper electrode UE.

Next, as shown in FIG. 7E, a first etching step may be performed tolocally remove the first to third insulating layers 10, 20, and 30. Forexample, the first and second contact holes CH1 and CH2 may be formed toexpose at least a portion of the input and output regions of the firstsemiconductor pattern OSP1, respectively. In an embodiment, the firstetching step may be performed to locally remove the first to thirdinsulating layers 10 to 30 in the bending region BA to form a firstupper groove GV-21. In an embodiment, the first etching step may use asingle mask to form the first and second contact holes CH1 and CH2 onthe non-bending region NBA as well as the first upper groove GV-21 onthe bending region BA, thereby reducing the number of the mask requiredto fabricate the display panel.

Thereafter, as shown in FIG. 7F, a second preliminary semiconductorpattern OSP2-P may be formed on the third insulating layer 30. Thesecond preliminary semiconductor pattern OSP2-P may be formed of orinclude a metal oxide semiconductor material. The formation of thesecond preliminary semiconductor pattern OSP2-P may include forming ametal oxide semiconductor layer and performing a patterning process onthe metal oxide semiconductor layer. In an embodiment, the secondpreliminary semiconductor pattern OSP2-P may be formed to have aconductive property.

In certain embodiments, the process steps described with reference toFIG. 7E and FIG. 7F may be performed in a different order. For example,the first etching step for forming the first and second contact holesCH1 and CH2 and the first upper groove GV-21 may be performed after theformation of the second preliminary semiconductor pattern OSP2-P.

Next, as shown in FIG. 7G, an electrode formation step may be performedto form electrodes DE1, SE1, SE2, and DE2 on the third insulating layer30. The formation of the electrodes DE1, SE1, SE2, and DE2 may includeforming a conductive layer using a deposition process and performing apatterning process on the conductive layer.

The patterning of the conductive layer may be performed by a plasmaprocess using an etching gas. In an embodiment, the etching gas mayinclude an oxygen-containing material, and in this case, oxygen plasmaproduced from the etching gas may be used for the plasma process. Theetching gas may be used to reduce a concentration of hydrogen in aregion of the second preliminary semiconductor pattern OSP2-P that isnot veiled by the second input electrode DE2 and the second outputelectrode SE2. Thus, the unveiled region of the second preliminarysemiconductor pattern OSP2-P that is located between the second inputelectrode DE2 and the second output electrode SE2 may have an electricalresistance that is higher than that of the veiled regions of the secondpreliminary semiconductor pattern OSP2-P that are located under thesecond input electrode DE2 and the second output electrode SE2. Forexample, the unveiled region of the second preliminary semiconductorpattern OSP2-P may be changed to have a semiconductor-like bandstructure, thereby serving as a channel region. That is, by treating thesecond preliminary semiconductor pattern OSP2-P having the conductiveproperty with the etching gas, the second semiconductor pattern OSP2that has at least a portion of the semiconductor-like band structure maybe formed. The second semiconductor pattern OSP2 may include the channelregion that has the semiconductor-like band structure, and the input andoutput regions that are spaced apart from each other with the channelregion interposed therebetween.

Thereafter, as shown in FIG. 7H, a preliminary fourth insulating layer40-I may be formed in both of the non-bending region NBA and the bendingregion BA to cover the third insulating layer 30 and the electrodes DE1,SE1, SE2, and DE2. The preliminary fourth insulating layer 40-I mayinclude a portion filling at least a portion of the first upper grooveGV-21.

Next, as shown in FIG. 7I, a second etching step may be performed topartially remove the preliminary fourth insulating layer 40-I. Thesecond etching step may be performed to form a contact hole CH3-40 thatpenetrates through the preliminary fourth insulating layer 40-I andexposing at least a portion of the first output electrode SE1.

In an embodiment, the second etching step may partially remove thepreliminary fourth insulating layer 40-I in the bending region BA andthereby forming a second upper groove GV-22. In an embodiment, thesecond etching step may use a single mask to form the contact holeCH3-40 in the non-bending region NBA as well as the second upper grooveGV-22 in the bending region BA, thereby reducing the number of the maskrequired to fabricate the display panel.

As shown in FIG. 7I, the second upper groove GV-22 and the first uppergroove GV-21 may be formed to have inner side surfaces aligned to eachother, but the inventive concept is not limited thereto. For example, asshown in FIG. 5, the third groove GV-3 may be formed in the preliminaryfourth insulating layer 40-I to expose at least a portion of the topsurface of the third insulating layer 30.

As shown in FIG. 7J, a third etching step may be performed to partiallyremove the inorganic layers BRL and BFL in the bending region BA. Forexample, in the third etching step, an etching gas may be used topartially remove the barrier layer BRL and the buffer layer BFL in thebending region BA and thereby forming the first groove GV-1 in thebending region BA. A top surface of inorganic layers including thebarrier layer BRL and the buffer layer BFL may be partially exposeddepending on an etching time or an etchant. In certain embodiments, thefirst groove GV-1 may be formed to have an inner side surface aligned tothat of the first upper groove GV-21.

In an embodiment, the third etching step for forming the first grooveGV-1 and the second etching step for forming the second upper grooveGV-22 may be performed in a successive manner. The third etching stepand the second etching step may constitute a single process that isperformed using the same mask, but may differ from each other in termsof an exposure time to an etching gas or a material of the etching gas.Thus, the number of masks used in the etching process may be reduced,thereby simplifying the fabrication process, and reducing thefabrication cost.

As shown in FIGS. 7K and 7L, after the second etching step, the fourthinsulating layer 40 may be formed by performing a thermal treatment HTon the preliminary fourth insulating layer 40-I. The thermal treatmentHT may be performed to thermally cure the channel region of the secondsemiconductor pattern OSP2 that is covered with the preliminary fourthinsulating layer 40-I. A stress may be exerted on the channel region ofthe second semiconductor pattern OSP2, when a conductive layer to beused as the second input electrode DE2 and the second output electrodeSE2 is deposited, for example, by a physical deposition process. In anembodiment, the thermal treatment HT may stably cure defects that mayhave been formed in the channel region of the second semiconductorpattern OSP2. Furthermore, the thermal treatment HT may be performed toprevent hydrogen atoms in the preliminary fourth insulating layer 40-Ifrom flowing into the channel region of the second semiconductor patternOSP2.

In an embodiment, the thermal treatment HT may be performed at a hightemperature of about 300° C. or higher. The thermal treatment HT mayinclude an annealing process that is gradually performed for a specificprocess time. According to an embodiment of the inventive concept, thefabrication method of the display panel may further include the thermaltreatment HT to be performed after the formation of the preliminaryfourth insulating layer 40-I to improve reliability of the secondsemiconductor pattern OSP2 and stabilize electric characteristics of thesecond thin-film transistor T2.

Next, as shown in FIG. 7M, the fifth insulating layer 50 may be formedon the fourth insulating layer 40. The fifth insulating layer 50 may beformed to overlap the non-bending region NBA and the bending region BA.The fifth insulating layer 50 may include a portion that is provided inthe first groove GV-1 and the second groove GV-2. The fifth insulatinglayer 50 may be formed to partially fill the contact hole CH3-40.

In an embodiment, the fifth insulating layer 50 may be formed, after thethermal treatment step on the fourth insulating layer 40. In a casewhere the fifth insulating layer 50 is formed of a polymer resin such aspolyimide, the fifth insulating layer 50 may be damaged during thethermal treatment HT. According to an embodiment of the inventiveconcept, a step of forming a layer containing an organic material (e.g.,the fifth insulating layer 50) may be postponed until the thermaltreatment HT on the fourth insulating layer 40 is finished to preventthe fifth insulating layer 50 from being damaged by the thermaltreatment HT, and thereby improving reliability of the fabricationprocess.

As shown in FIG. 7N, a fourth etching step may be performed to remove aportion of the fifth insulating layer 50. For example, a contact holeCH3-50 may be formed in the fifth insulating layer 50 to expose at leasta portion of the first output electrode SE1 that is covered with thefifth insulating layer 50. The contact hole CH3-50 of the fifthinsulating layer 50 may be aligned to the contact hole CH3-40 of thefourth insulating layer 40. The contact holes CH3-40 and CH3-50 may beconnected to each other to form a single contact hole that is defined asthe third contact hole CH3.

As shown in FIG. 7O, the connection electrode CNE may be formed on thefifth insulating layer 50. The process of forming the connectionelectrode CNE may also be used to form the portion of the signal line SLthat overlaps the bending region BA. As described above, the connectionelectrode CNE and the signal line SL may be two parts of a single objector may be two separate objects that are spaced apart from each other,but the inventive concept is not limited thereto.

As shown in FIG. 7P, the sixth insulating layer 60 may be formed on thefifth insulating layer 50 to cover not only the connection electrode CNEbut also the portion of the signal line SL that overlaps the bendingregion BA. The fourth contact hole CH4 may be formed in the sixthinsulating layer 60 to expose at least a portion of the top surface ofthe connection electrode CNE.

As shown in FIG. 7Q, the organic light emitting diode OLED may be formedon the sixth insulating layer 60 in the non-bending region NBA. Thefirst electrode AE may be formed on the sixth insulating layer 60 andmay be connected to the connection electrode CNE through the fourthcontact hole CH4. The pixel definition layer PDL may be formed on thesixth insulating layer 60 to expose a center portion of the firstelectrode AE. A preliminary pixel definition layer may be formed on thesixth insulating layer 60 and may be patterned to form the pixeldefinition layer PDL with the opening OP.

Thereafter, the hole control layer HCL, the light-emitting pattern EML,the electron control layer ECL, and the second electrode CE may besequentially formed in the non-bending region NBA of the pixeldefinition layer PDL. The hole control layer HCL, the light-emittingpattern EML, the electron control layer ECL, and the second electrode CEmay overlap at least the display region DP-DA (e.g., see FIG. 2), whenviewed in a plan view.

The encapsulation layer TFE may be formed on the second electrode CE. Asfor the encapsulation layer TFE, an organic encapsulation layer and/oran inorganic encapsulation layer may be formed by a deposition or inkjetprinting process. The encapsulation layer TFE may be formed in thenon-bending region NBA and may not be formed in the bending region BA,but the inventive concept is not limited thereto.

FIG. 8A is a graph showing current-voltage characteristics of athin-film transistor according to a comparative example, and FIG. 8B isa graph showing current-voltage characteristics of a thin-filmtransistor according to an embodiment of the inventive concept. FIG. 8Ais a graph showing current-voltage characteristics of a thin-filmtransistor that has been treated by a thermal treatment at a relativelylow temperature (e.g., 300° C. or lower), and FIG. 8B is a graph showingcurrent-voltage characteristics of a thin-film transistor (e.g., thesecond thin-film transistor T2 described with reference to FIG. 3B) thatis treated by a thermal treatment at a relatively high temperatureaccording to an embodiment of the inventive concept. In FIGS. 8A and 8B,the voltage V_(G) represents a gate voltage applied to a gate electrodeof a thin-film transistor, and the current I_(DS) represents an amountof electric current flowing through a channel region of the thin-filmtransistor applied with the gate voltage. The thin-film transistors forFIGS. 8A and 8B have been fabricated to have substantially the samefeatures and structure, except for a difference in process temperaturein the thermal treatment step. For convenience in illustration, curvesmeasured from each thin-film transistor at different times are plottedin FIGS. 8A and 8B. Hereinafter, the inventive concept will be describedin more detail with reference to FIGS. 8A and 8B.

In the comparative example of FIG. 8A, the thermal treatment step on thethin-film transistor is performed at a low temperature (e.g., of 300° C.or lower or of about 250° C.) that may be too low to cause damage to thefifth insulating layer 50. First to fifth curves PL1, PL2, PL3, PL4, andPL5 in FIG. 8A are sequentially measured at different times. For thethin-film transistor according to the comparative example, as shown inFIG. 8A, as the process time is increased, the curve gradually movesleftward (i.e., from the first graph PL1 to the fifth graph PL5). Adifference in a threshold voltage between the first curve PL1 showing aninitial current-voltage property and the fifth curve PL5 showing thelastly-measured current-voltage property is about −5.68V. That is, in acase where, as in the comparative example, the thin-film transistor isnot treated at a sufficiently high temperature, the thin-film transistormay suffer from poor uniformity in electric characteristics and a shortlife.

By contrast, the current-voltage graph of FIG. 8B is obtained from athin-film transistor including a semiconductor pattern that is thermallytreated at a temperature of about 380° C. As shown in FIG. 8B,current-voltage curves that are measured from the thin-film transistorat different times converge to a single indistinguishable curve PL-T.

In FIG. 8B, a difference in a threshold voltage between the curveshowing an initial current-voltage property and the curve showing thelastly-measured current-voltage property is about −0.20V. This showsthat the thin-film transistor according to an embodiment of theinventive concept has an invariant current-voltage property or uniformelectric characteristics. According to an embodiment of the inventiveconcept, since the organic layer (e.g., the fifth insulating layer 50 ofFIG. 3B) is formed after the formation of the fourth insulating layer 40to thermally treat the fourth insulating layer 40 at a high temperatureof 300° C. or higher while preventing the fifth insulating layer 50 frombeing damaged. Thus, the thin-film transistor can be fabricated to haveimproved electric characteristics and a longer life. Furthermore, themethod according to an embodiment of the inventive concept may stablyprovide a display panel with high reliability and improved electriccharacteristics.

FIG. 9 is a sectional view illustrating a portion of a display panelaccording to an embodiment of the inventive concept. For convenience indescription, a region corresponding to FIG. 7Q is illustrated in FIG. 9.Hereinafter, an embodiment of the inventive concept will be described inmore detail with reference to FIG. 9. For concise description, anelement previously described with reference to FIGS. 1A to 8B may beidentified by the same reference number without repeating an overlappingdescription thereof.

In the display panel shown in FIG. 9, the connection electrode CNE andthe sixth insulating layer 60 may be omitted. Accordingly, the firstelectrode AE may be directly provided on the fifth insulating layer 50and may be connected to the first output electrode SE1 through the thirdcontact hole CH3. A signal line SL-DL may include a portion thatoverlaps the bending region BA and is directly provided on the fifthinsulating layer 50.

The portion of the signal line SL-DL that overlaps the bending region BAmay be formed by the same process as that for the first electrode AE.The portion of the signal line SL-DL that overlaps the bending region BAand the first electrode AE may include the same material and may havethe same layer structure.

FIGS. 10A to 10D are sectional views illustrating a method offabricating a display panel according to an embodiment of the inventiveconcept. In order to avoid redundancy, some of the steps described withreference to FIGS. 7A to 7Q are illustrated in FIGS. 10A to 10D.Hereinafter, an embodiment of the inventive concept will be described inmore detail with reference to FIGS. 10A to 10D. For concise description,an element previously described with reference to FIGS. 1A to 9 may beidentified by the same reference number without repeating an overlappingdescription thereof.

As shown in FIG. 10A, the second preliminary semiconductor patternOSP2-P and the contact holes CH1 and CH2 may be formed in thenon-bending region NBA of the base layer BL, and the first upper grooveGV-21 may be formed in the bending region BA. The structure of FIG. 10Amay substantially correspond to that of FIG. 7F. For convenience indescription, the aforesaid technical features may be omitted below.

Thereafter, as shown in FIGS. 10B and 10C, a conductive layer CLL may beformed on the third insulating layer 30, and the conductive layer CLLmay be patterned using an etching gas ET to form the electrodes DE1,SE1, DE2, and SE2. The conductive layer CLL may be formed to cover thetop surface of the third insulating layer 30 and the top surface of thesecond preliminary semiconductor pattern OSP2-P. The conductive layerCLL may also be formed to fill the contact holes CH1 and CH2 and atleast a portion of the first upper groove GV-21.

The etching gas ET may contain a material capable of etching at least aportion of the conductive layer CLL. The etching gas ET may react withexposed regions of the conductive layer CLL that are not veiled by amask (not shown), and thus, the exposed regions of the conductive layerCLL may be removed. Other regions of the conductive layer CLL veiled bythe mask may not be etched, thereby forming the electrodes DE1, SE1,DE2, and SE2.

In an embodiment, the etching gas ET may not contain a chlorinecompound. As an example, the etching gas ET may contain a fluorocompound containing fluorine (F). For example, the etching gas ET maycontain sulfur hexafluoride (SF₆) or hexafluoro butyne (C₄F₆).

In a case where the fluoro compound is used, the second semiconductorpattern OSP2 containing an oxide semiconductor material may have arelatively slow etch rate, compared to a case where the chlorinecompound is used. For example, in a case where the fluoro compound isused in the etching process, the conductive layer CLL may have a higheretch rate than that of the second semiconductor pattern OSP2. Theconductive layer CLL may be formed of or include, for example,molybdenum (Mo).

If the conductive layer CLL contains titanium (Ti) to etch theconductive layer CLL, an etching gas containing a chlorine compound maybe used. The oxide semiconductor material may have a relatively highetch rate, when the chlorine compound is used in the etching process.Accordingly, in a case where the etching gas containing the chlorinecompound is used to pattern the conductive layer CLL, the secondsemiconductor pattern OSP2 containing the oxide semiconductor materialmay be easily damaged.

According to an embodiment of the inventive concept, the etching gas ETmay be chosen to contain the fluoro compound to prevent the exposedregions of the second semiconductor pattern OSP2 from being damaged bythe etching process for forming the electrodes DE1, SE1, DE2, and SE2and stably form the second semiconductor pattern OSP2.

As shown in FIG. 10D, the third contact hole CH3 may be formed in thefourth insulating layer 40, and the connection electrode CNE may beformed to be connected to the first output electrode SE1. Forconvenience in illustration, the connection electrode CNE is illustratedto be provided on the fourth insulating layer 40, but the inventiveconcept is not limited thereto.

Since the connection electrode CNE is formed after the formation of thefourth insulating layer 40, the connection electrode CNE may beprevented from being affected by the etching gas ET of FIG. 10B. Inaddition, the connection electrode CNE may be independently formed,regardless of the formation of the second semiconductor pattern OSP2 orother elements. For example, the connection electrode CNE may bepatterned, without a concern of damaging other elements, and thus, amaterial for the connection electrode CNE may be freely chosen.

In an embodiment, the connection electrode CNE may be formed of orinclude a material whose electric resistance is lower than the firstoutput electrode SE1. In this case, the first output electrode SE1 andthe second output electrode SE2 is formed using same material. Due tothe mutually dependent relationship between the first output electrodeSE1 and the second semiconductor pattern OSP2, there may be arestriction in a material for the first output electrode SE1, and thismay lead to deterioration in electric characteristics of the displaydevice. However, the connection electrode CNE having the low electricresistance may be used to improve the electric characteristics of thedisplay device. For example, the connection electrode CNE may allow theorganic light emitting diode OLED (e.g., see FIG. 3B) and the firstthin-film transistor T1 to be connected to each other with a low contactresistance to realize a display panel having improved electriccharacteristics.

According to an embodiment of the inventive concept, in a process offabricating a semiconductor device, in which semiconductor patternshaving different characteristics are provided, a thermal treatment maybe performed without causing a damage of an organic layer, therebyimproving electric characteristics of the semiconductor pattern andreliability of the fabrication process. Furthermore, the organic layermay be provided at a position that is not affected by a thermaltreatment, so that a display panel with a highly-reliable long-timethin-film device may be realized.

While example embodiments of the inventive concept have beenparticularly shown and described, it will be understood by one ofordinary skill in the art that variations in form and detail may be madetherein without departing from the spirit and scope of the attachedclaims.

What is claimed is:
 1. A method of fabricating a display panel,comprising: forming a silicon semiconductor pattern on a base layerincluding a first region and a second region that is extended from thefirst region, the silicon semiconductor pattern overlapping the firstregion; forming a first control electrode on the silicon semiconductorpattern, the first control electrode overlapping the siliconsemiconductor pattern with a first insulating layer interposedtherebetween; forming a second control electrode to overlap the firstregion and to be spaced apart from the first control electrode with asecond insulating layer interposed therebetween; forming an oxidesemiconductor pattern on the second control electrode to overlap thesecond control electrode with a third insulating layer interposedtherebetween; etching the first, second, and third insulating layers toform a first contact hole and a second contact hole exposing at least aportion of the silicon semiconductor pattern and a first groove thatoverlaps the second region; forming on the third insulating layer afirst input electrode and a first output electrode that are connected tothe silicon semiconductor pattern through the first and second contactholes, and a second input electrode and a second output electrode thatare connected to the oxide semiconductor pattern; forming a fourthinsulating layer on the third insulating layer to cover the first inputelectrode, the first output electrode, the second input electrode, andthe second output electrode; thermally treating the fourth insulatinglayer at a controlled temperature prior to forming any layer on thefourth insulating layer; forming an organic layer to cover the fourthinsulating layer; and forming on the organic layer an organic lightemitting diode that is connected to the first output electrode.
 2. Themethod of claim 1, wherein the thermal treating of the fourth insulatinglayer is performed at a temperature of about 300° C. or higher.
 3. Themethod of claim 2, wherein the organic layer comprises polyimide.
 4. Themethod of claim 1, wherein the etching of the first, second, and thirdinsulating layers is performed to simultaneously form the first andsecond contact holes and the first groove using a single mask.
 5. Themethod of claim 1, further comprising forming a second groove thatoverlaps the first groove in the fourth insulating layer after theforming of the fourth insulating layer, wherein the organic layer isformed to fill the first groove and the second groove.
 6. The method ofclaim 5, further comprising forming an inorganic layer between the firstinsulating layer and the base layer, wherein the forming of the secondgroove comprises forming a third groove that overlaps the first groovein the inorganic layer.
 7. The method of claim 1, further comprising:forming a third contact hole in the organic layer to expose a portion ofthe first output electrode; forming a connection electrode on theorganic layer to be connected to the first output electrode through thethird contact hole; and forming an upper organic layer on the organiclayer to cover the connection electrode, wherein the organic lightemitting diode is connected to the connection electrode through theupper organic layer.
 8. The method of claim 7, wherein the connectionelectrode is formed of a material that is different from the firstoutput electrode.
 9. The method of claim 8, wherein the connectionelectrode is formed of a material whose resistance is lower than that ofthe first output electrode.
 10. The method of claim 1, wherein theforming of the first input electrode, the first output electrode, thesecond input electrode, and the second output electrode comprises:forming a conductive layer on the third insulating layer to cover theoxide semiconductor pattern; and patterning the conductive layer usingan etching gas, wherein the etching gas contains a fluoro compound. 11.The method of claim 10, wherein the conductive layer has a higher etchrate than the oxide semiconductor pattern in the patterning of theconductive layer using the etching gas.
 12. A display panel, comprising:a base layer including a first region and a second region that is bentfrom the first region along a predetermined bending axis; a firstthin-film transistor provided in the first region, the first thin-filmtransistor comprising a crystalline silicon semiconductor pattern, afirst control electrode, and a first input electrode and a first outputelectrode that are coupled to the crystalline silicon semiconductorpattern and are spaced apart from each other with the first controlelectrode interposed therebetween; a second thin-film transistordisposed in the first region to have a bottom gate structure, the secondthin-film transistor comprising a second control electrode, an oxidesemiconductor pattern disposed on the second control electrode, and asecond input electrode and a second output electrode that are in contactwith the oxide semiconductor pattern and are spaced apart from eachother; a passivation layer disposed in the first region and the secondregion to cover the first thin-film transistor and the second thin-filmtransistor and to include a first groove that overlaps the secondregion; a plurality of inorganic layers disposed between the passivationlayer and the base layer to include a second groove that overlaps thefirst groove; an organic layer disposed in the first region and thesecond region and on the passivation layer to cover inner surfaces ofthe first and second grooves; and an organic light emitting diodedisposed on the organic layer and in the first region and electricallyconnected to the first thin-film transistor, wherein a plurality ofinorganic layers are disposed to expose a portion of a top surface ofthe base layer, and the organic layer is disposed to be in contact withthe portion of the top surface of the base layer.
 13. The display panelof claim 12, wherein the second input electrode and the second outputelectrode comprise molybdenum.
 14. The display panel of claim 12,further comprising: an upper organic layer disposed between the organiclayer and the organic light emitting diode; and a connection electrodedisposed between the upper organic layer and the organic layer andcoupled to each of the organic light emitting diode and the first outputelectrode, wherein the connection electrode comprises a material that isdifferent from that of the first output electrode.
 15. The display panelof claim 14, wherein the connection electrode comprises a material whoseresistance is lower than that of the first output electrode.
 16. Thedisplay panel of claim 14, further comprising a signal line disposed inthe second region and overlapping the first groove and the secondgroove, wherein the signal line is disposed on the same layer as theconnection electrode.
 17. The display panel of claim 12, furthercomprising a pixel definition layer disposed on the organic layer andincluding an opening, wherein the organic light emitting diode isdisposed in the opening, wherein the pixel definition layer overlaps thefirst region and the second region and comprises an organic material.18. The display panel of claim 17, wherein the pixel definition layerfurther comprises a recessed portion on an inner surface of the opening.19. The display panel of claim 12, wherein the passivation layer is incontact with the oxide semiconductor pattern.
 20. A display panelcomprising: a base layer including a first region and a second regionthat is bent from the first region along a predetermined bending axis; afirst thin-film transistor provided in the first region, the firstthin-film transistor comprising a crystalline silicon semiconductorpattern, a first control electrode, and a first input electrode and afirst output electrode that are coupled to the crystalline siliconsemiconductor pattern and are spaced apart from each other with thefirst control electrode interposed therebetween; a second thin-filmtransistor disposed in the first region to have a bottom gate structure,the second thin-film transistor comprising a second control electrode,an oxide semiconductor pattern disposed on the second control electrode,and a second input electrode and a second output electrode that are incontact with the oxide semiconductor pattern and are spaced apart fromeach other; a passivation layer disposed in the first region and thesecond region to cover the first thin-film transistor and the secondthin-film transistor and to include a first groove that overlaps thesecond region; a plurality of inorganic layers disposed between thepassivation layer and the base layer to include a second groove thatoverlaps the first groove; an organic layer disposed in the first regionand the second region and on the passivation layer to cover innersurfaces of the first and second grooves; an organic light emittingdiode disposed on the organic layer and in the first region andelectrically connected to the first thin-film transistor; and a signalline that is disposed in the second region and overlapping the firstgroove and the second groove, wherein each of etch rates of the secondinput electrode and the second output electrode that are etched by afluoro compound are higher than that of the oxide semiconductor pattern,and wherein the signal line is disposed on the same layer as the secondoutput electrode.
 21. The display panel of claim 20, wherein the signalline comprises a plurality of patterns that are disposed in the secondregion and are spaced apart from each other in a direction crossing thebending axis.